Help with DIY LED fixture

I read a lot about this, but I still need your help because I really want to make my own LED fixture, so I'll appreciate every help you can give me.

Let's begin!

I have a new tank, it's about 43x19x19 inches (110x50x50 cm) and I want to set it up as an hi-tech tank, that allows me to keep every kind of plant I want; that's what I'm thinking about:

a big finned heatsink, 30"x12" (90x30 cm), 1.6" thick (4 cm), with some Cree XM-L leds (I can change the measures of the heatsink if you think it's better, that's just what I was planning), I would like it to be passive cooled..

LED distribution:

The led spacing would be 4" and each of the 3 row is 4" from another too; yellow dots are Warm White leds, and white dots are Cool White.

Each row would be driven at 1750mA separately, no dimming for now, maybe in the future.. I was considering not to use optics/lenses since they're considerably hard for me to find, so I should keep the leds really close to the water surface (4-5"), so about 20" from the substrate.

What do you think? Too much light? Too low? Impossible to do it without lenses?

You are definitely in enough light to do anything you want territory if all those are XM-L. I am pretty sure you going to have to put it higher than your original plan. I would definitely look into adding dimming now though.

I read a lot about this, but I still need your help because I really want to make my own LED fixture, so I'll appreciate every help you can give me.

Let's begin!

I have a new tank, it's about 43x19x19 inches (110x50x50 cm) and I want to set it up as an hi-tech tank, that allows me to keep every kind of plant I want; that's what I'm thinking about:

a big finned heatsink, 30"x12" (90x30 cm), 1.6" thick (4 cm), with some Cree XM-L leds (I can change the measures of the heatsink if you think it's better, that's just what I was planning), I would like it to be passive cooled..

LED distribution:

The led spacing would be 4" and each of the 3 row is 4" from another too; yellow dots are Warm White leds, and white dots are Cool White.

Each row would be driven at 1750mA separately, no dimming for now, maybe in the future.. I was considering not to use optics/lenses since they're considerably hard for me to find, so I should keep the leds really close to the water surface (4-5"), so about 20" from the substrate.

What do you think? Too much light? Too low? Impossible to do it without lenses?

Sorry for my english and for the bad scheme..

REALLY THANKS IN ADVANCE!!

Alessio

a couple of things.. 1750mA driver????

also if it was me, I'd stick one type of white per channel..
you can "control" the color temp..
Use LDD PWM dimming drivers and buy a $50 Typhon from StevesLEDs..

The 10 WW are not a problem.. 17 whites are a bit of an issue..

Using a 48V seperate power supply and Ldd's @ $7 each, I'd look at splitting into at least 3 channels..Adding a channel costs about $7 US (one driver)

Use 1000mA driver.. Better W/lm ratio...and easier to cool..

Assume 3.4V per LED (really more like 3.0 @1000mA) in series and 3V "loss" w/ a Meanwell LDD..
48V PS usually can be "tweaked" to about 51V..
Limit yourself to 13LED's/per channel..IF using 3 you can squeeze in 15/channel (1000mA drive current)

I assume you have some driver in mind.. which is it?

Oh as to dimming.. Best to "plan ahead".. since driver swapping is poor economics..

no optics, low to tank is fine, scheme fine,
Slight mod for channel balance but it would be dependent if you plan to dim.. The overall tone may be a bit "warm" (straight on full) but that is user preference .. or not.
12WW:14 cool white

Thanks for your help jeffkrol, I really appreciate it! But gus6464 hits the point: at least from what I read, here on plantedtank and generally around the internet, is not worth to run XM-L at "low" current.. Probably even at 1A they're still better than other leds, but running them at 1A means that I'll have almost half light than I was planning..

But you're surely right when you say that I should drive different whites on separate drivers and not mix them in the same series!

gus6464, even if I'm from Italy, I'll not buy anything here, since I can't find anything. I'll buy from a shop overseas. (don't know if I can put a link)

I really would be able to have a dimming system, I love the controllers like Typhon from SteveLEDs, but I don't find the correct drivers to do it, not only to regulate the current to the leds but mostly to have a sunrise/sunset system.

From the shop I'm going to buy, I find just an LDD-700HW.

I could also change to a 1400mA version of the driver, or mix them and run (for example) CW at 1400mA and WW at 1750mA, i don't know what to do Still no dimming though.

Well another option is to go with meanwell LDD-1500L. They are 36V but can do up to 1500ma. So 3 of these can power all your LEDs. Put all the warm whites on one driver and then put the cool whites on the other two drivers.

The real problem for me, is to find availability of so many products. Only for the LDD drivers, it would cost me more for the shipping than for the drivers!

I really want it to be dimmable, but what I have to do is to find a store that has almost everything I need. I can't make 3-4 international shipments.. It would cost more than the fixture itself hehe
If you know a store that has almost everything, just PM me! (the only thing that i've found on a local store, is the heatsink)

@jeffkrol: seriously speaking, do you think that adding cyan-660nm leds would be necessary/useful?

Whites, for the most part (newer high CRI ones are better) are deficient in the lower reds..
though the "effect" is arguable.. 660nm is the primary chlorophyll absorption band..and it adds for great "sunsets" when put on a separate channel to be blended w/ warm whites..

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